They're using the ladder exit function entity (can't recall the exact name). When you hit the top or bottom of a ladder, if you are facing the general exit direction it'll kick you off to a safe spot. No need to jump or hit E. But if you're used to not having this happen you end up fighting it and that's when the falling happens. It's the same way as how the ladders in HL2 onwards works, although I think Valve deployed it better, taking into account its downsides.
The jumping in this is really hit and miss, as are the ladders. Pressing E to get off the ladders is often the only way to avoid a plunge to your death, but it's markedly worse than the original.
Gray, if you're talking about the part where you have to go down a load of suspended crates, you don't have to jump for most of it, you walk off from one to another.